Method of softening shoe stiffeners



JAMES L. MGCLELLAN, GE BROUKLINE, MASSACHUSETTS.

METHUID 01F SOJETENING SHQE STIFFEHEBQ.

neonate.

Ito Lbrawing.

Softening Shoe Stifieners, of which the following is a specification.

This invention relates to blanks adapted to stiffen portions of shoe uppers, such as.

the toe portion and the heel-portion, the blank being composed of fibrous material such as felt, and provided with a stiffening composition which is adapted to be softened,

"' and to harden after an upper with which the blank is associated has been applied to a last and the blank has been suitably shaped by the last.

This invention relates particularly to the improved shoe stiffener disclosed by my pending application, Serial No. 329,935, filed @ctober 11, 1919, now Patent No. 1,3a8,968, granted September 28, 1920, of a blank of fibrous material, and a filling which consists of a celluloid-resin solution diffused throughout the blank.

I have heretofore softened the said composition by a moderate degree of heat, as by immersion in water at a temperature of 180 de recs, F.

The object of the presentinvention is to enable a blank characterized as set forth in the above-mentioned application to be softened more satisfactorily than heretofore,

without the employment of heat.

The invention consists in the improved method hereinafter described and claimed.

In carrying out my invention, I immerse a blank of fibrous material containing asuitable stiifenin composition of celluloidresin as describe in my former a plication, in a bath composed of a comblnation of chemicals as described below.

I have found that by combining suitable proportions of active solvents and non-solvents of celluloid that I am able to effect complete softening of the impregnated blank, without allowing an appreciable quantity of the filling material to be dissolved out. l have found that latent solvents of celluloid which are soluble in the solvents or non-solvents, or in a combination of the two, also exert a Specification of Letters Patent.

Patented Mar. 57, 1922.

Application filed April 83, 3.920. serial Cato. 3769M.

marked softening action on the impregnated blank.

Following is a list of the common active solvents of celluloid: ethyl acetate, acetone.

A common non-solvent is water. The common latent solvents are :-camphor, acetanilid, and'beta naphthol.

There are hundreds of others of each of these groups, but these are the common ones.

The proportions of active-solvent and non-solvent are adjusted to give the best softening action, and at the same time to prevent as much of the filling material from going into solution as possible. The active solvent is the softening agent, while the non-solvent acts as a retarder, and tends to lid inhibit the filling material from going into solution. Where the latent solvent is used,

acts an an intensifier of the solvent achorn and consequently increases speed of softening.

The method of softening consists in immersing the blank, impregnated with the celluloid-resin compound, as described in my former patent, in one of the solutions described above, or in solutions having similar reactions. The filling in the immersed blank is softened by the penetration of the solvent contained in the bath into the fibers of the blank; such penetration causing a partial solution of the filling material, so

that the blank quickly becomes soft and pliable, and capable of being molded on a last. a

As soon as the blank becomes soft and pliable, it is removed from the bath and lasted into a shoe. Care should be taken not to allow the blank to remain in the bath beyond this point, or some of the filling material is liable to be dissolved out.

The speed of the penetration of the solvents into the fibrous material of the blank, and therefore the speed of the softening, depends on the closeness with which the ma terial is woven or pressed together. For instance, in the case of felt, which is merely fibers pressed to ether, the penetration isill thus causing slower evaporation of the solvents.

(b) The time may be shortened by the reverse of the above methods, namely: I

(1) Keeping lasted shoes in a warm place to increase the evaporation of solvents- (2) Increase percentage of lower boiling solvents in softening liquid, and thus cause more rapid evaporation of the solvents.

The followin a formula for a solution l have invente for the proper softening of the impregnated blanks. Active solvent: acetone, 100 parts (by weight). Non-solvent: water, 10 parts (by weight). Latent solvent: camphor, 20 parts (by weight).

g The advantages ct this method of softening over that of softening by heat are,-

(1) The leather of the shoe is not liable to be injured or cracked, since, as no heat is used, there is no danger of overheating, as is the case where steam or other forms of heat are used to soften.

(2) The blanks stay soft and pliable tor a greater length of time with this method, so, therefore, there is more time allowed for lasting, and the blanks can bemore carefully and smoothly shaped to the last, than is the case where heat is used to soften.

F or in the latter case, hardening takes place very rapidly. With this new process, hardening may be slowed up, to take place in one half hour, or any time up to twenty-four hours, or longer, according to the softening mixture iaoesie used. The more volatile the solvent, the quicker its evaporation, and hence, the more rapid hardening of the blank.

(2%)- This-method eliminates the second softening process in shoe factories, since the hardening can be delayed for twenty-four hours, which is suihcient time for the partially lasted shoes. to passto the final lasting-process. Whenthe heat method is used, it is necessary to sotten the blanks twice.

T claim:

1. The method of softening a shoe-stitfener blank of fibrous material, containing a celluloid-resin filling, said method consisting in immersing the blank in a bath which includes an active solvent oir' celluloid, and a non-solvent (it celluloid.

2. The method of softening a shoe-stif fener blank of fibrous material, containing a celluloid-resin filling, said method consisting in immersing the blank in a bath which includes an active solvent of celluloid, a non-solvent of celluloid, and a latent solvent ct celluloid.

3. The method of softening a shoe-stittener blank of fibrous material, containing a celluloid-resin filling, said method consisting in immersing" the blank in a bath which includes acetone as an active solvent of celluloid, and a non-solvent of celluloid. I

4t. The method of softening a shoe-stifiener blank 0t fibrous material, containing a celluloid-resin filling, said method consisting in immersing the blank in a bath which includes an active solvent of celluloid, and water as a non-solvent of celluloid.

5. The method of softening a shoe-stiffener blank of fibrous material, containing a celluloid-resin filling, said method consisting in immersing the blank in a bath which includes an active solvent of celluloid, a non-solvent of celluloid, and camphor as a latent solvent of celluloid.

Tn testimony whereof I have allixed my signature.

JAMES L. McCLELLAN. 

